1. Field of the Invention
The present invention relates to a super-compact motor suitable for arrival or destination informing apparatus in a portable telephone, for example.
2. Related Background Art
Among communication apparatuses for portable equipments, an alarming device for informing the user of communication by vibration is already known. In such a pager motor, a weight having an imbalanced mass is attached to an output shaft of the motor so that vibration is generated when the motor is rotatingly driven. Such motors will be widely used in the future. It is desirable that such a motor be made more compact as the portable equipment becomes small-sized.
In the past, as a type suitable for a compact motor, a brushless type is known. Among the motors of brushless type, there are the following stepping motors having a simple circuit.
A compact cylindrical stepping motor as shown in FIG. 19 is known. Stator coils 105 are concentrically wound around corresponding bobbins 101. The bobbins 101 are pinched and secured between corresponding stator yokes 106 from an axial direction, and the stator yokes 106 have stator teeth 106a and stator teeth 106b arranged alternately along a circumferential direction of inner surfaces of the bobbins 101. The stator yokes 106, integral with the stator teeth 106a or 106b, are secured to cases 103 to constitute a stator 102.
A flange 115 and a bearing 108 are secured to one of a set of cases 103, and another bearing 108 is secured to the other case 103. A rotor 109 comprises a rotor magnet 111 secured to a rotor shaft 110, and radial gaps are defined between the rotor magnet 111 and the stator yokes 106 of the stator 102. The rotor shaft 110 is rotatably supported by the bearings 108.
Further, a stepping motor driven by a single coil and widely used with a clock as shown in FIG. 21 is also known. A rotor 201 comprises a permanent magnet and is associated with a stator 203 and a coil 204.
However, in the conventional compact stepping motor shown in FIG. 19, since the cases 103, bobbins 101, stator coils 105 and stator yokes 106 are concentrically arranged around the rotor, the entire dimension of the motor becomes great. Further, as shown in FIG. 20, since magnetic flux generated by energization of the stator coil 105 mainly passes through an end face 106a1 of the stator tooth 106a and an end face 106b1 of the stator tooth 106b, the magnetic flux does not act on the rotor magnet 111 effectively, with the result that a high output of the motor cannot be obtained.
Also regarding the motor shown in FIG. 21, magnetic flux generated by energization of the coil is concentrated into the smallest gap between the stator 203 and the coil 204 and does not act on the magnet effectively.
In a pager motor in which the weight having an mass imbalanced with respect to a rotational center is attached to the output shaft of the motor to convert rotation of the motor into vibration, since the weight is attached on an outer surface of the motor body, the assembling must be effected very carefully so that lead wires, a flexible print substrate, and the like are not positioned in a rotation path of the weight.
A destination informing device of the wrist-watch type has also been proposed, as disclosed in Japanese Patent Laid-Open No. 8-146161 (1996).
In this case, since a weight is secured to an output shaft protruded outwardly from a motor, the entire motor including the weight must be covered by a case, which makes compactness of the destination informing device difficult to achieve. Further, when the user wears the communication device on a portion of his body where vibration can easily be detected, the presence of such a device is not preferable from the viewpoint of fashion. An example is shown in FIG. 22. In FIG. 22, the reference numeral 300 denotes a motor; 301 denotes a weight; 302, 303 denote cases of the destination informing device; and 304 denotes a motor attaching member for attaching the motor 300 to the case 303. Since the weight 301 is associated with the cases 302, 303 via the motor 300 and the motor attaching member 304, in FIG. 22, great gaps a, b must be maintained between the weight 301 and the cases 302, 303. Thus, the thickness t of the destination informing device is increased.
In communication device of the wrist-watch type, if the user has already worn his wrist watch on his wrist, the fact that both the wrist watch and the communication device are worn on his wrist is not preferable from the viewpoint of fashion. Further, although it is considered that a communication device is incorporated into a wrist watch itself, since the design, the size, and the color of the watch are limited, it is not preferable from the viewpoint of fashion.
As a compact motor for a communication apparatus, a cored AC motor or coreless AC motor of brush type can be used. However, since such a motor has a relatively large number of constructural parts, if the motor is made super-compact, it becomes difficult to manufacture and assemble such constructural parts, which leads to an increase in cost.
The inventors have proposed a motor solving the disadvantage of the conventional motor shown in FIG. 19, as disclosed in U.S. Pat. No. 5,831,356.
In this proposed motor, a cylindrical rotor comprises permanent magnets equidistantly disposed in a circumferential direction and having alternate magnetic poles; a first coil, a rotor and a second coil are sequentially disposed in an axial direction of the rotor; a first outer magnetic pole and a first inner magnetic pole which are excited by the first coil an are opposed to outer and inner peripheral surfaces of the rotor, and a second outer magnetic pole and a second inner magnetic pole, which are excited by the second coil are opposed to the outer and inner peripheral surfaces of the rotor; and a rotary shaft (rotor shaft) extends from the interior of the cylindrically arranged permanent magnets.
Although such a motor can have a high output and a small outer dimension, since the diametrical dimensions of the inner magnetic poles are small, it is difficult to manufacture magnetic teeth. Further, it has been requested that a stable output having no vibration be obtained from a motor having a small diametrical dimension.
To this end, the inventors have recently proposed a motor in which inner magnetic poles have configuration having good workability, as described in U.S. patent application Ser. No. 08/994,994, and the inventors have also proposed a rotor in which output transmitting means, such as a gear or a pulley, can easily be attached to a rotary shaft having a small diametrical dimension and a stable output having no vibration can be obtained, as described in U.S. patent application Ser. No. 09/022,474.
Recently, it has been requested to provide a motor having a high output and super-compact size.
To this end, the inventors have recently proposed a motor constructed as a single phase motor to achieve high output and super-compact size, as described in U.S. patent application Ser. No. 09/293,063.
In recent years, it has been requested that such a motor having a high output and super-compact size be applied to a destination informing apparatus.
The present invention aims to eliminate the above-mentioned conventional drawbacks, and an object of the present invention is to provide a motor having a configuration suitable for a communication apparatus, in which a high output can be obtained with a simple construction.
Another object of the present invention is to provide a motor for a communication apparatus, in which the motor is constructed as a single phase motor to stabilize initial positioning of a rotor.
The other objects and features of the present invention will become more apparent upon consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings.